The primary goal of safety engineering is to protect persons from hazard sources such as, for example, machines in an industrial environment represent. The machine is monitored with the aid of sensors and accordingly, if a situation is present in which a person threatens to come dangerously close to the machine, a suitable securing measure is taken.
3D sensors are inter alia used for the monitoring. They initially include 3D cameras in different technologies, for example stereoscopy, triangulation, time of flight, or evaluation of the interference of passive two-dimensional patterns or of projected illumination patterns. Such 3D sensors, in contrast to a conventional two-dimensional camera, record images that include a distance value in their pixels. These depth-resolved or three-dimensional image data are also called a depth map. Laser scanners are furthermore known that scan in two directions or in all three directions and that likewise detect three-dimensional image data over the respective scanning angles and the measured distance. The higher instrument and evaluation effort for generating three-dimensional image data in comparison with a two-dimensional image detection is justified by the additional information in a number of applications.
Sensors used in safety technology or for the protection of persons have to work particularly reliably and must therefore satisfy high safety demands, for example the standard EN13849 for safety of machinery and the machinery standard IEC61496 or EN61496 for electrosensitive protective equipment (ESPE). To satisfy these safety standards, a series of measures have to be taken such as a secure electronic evaluation by redundant, diverse electronics, functional monitoring or especially monitoring the contamination of optical components.
The common securing concept provides that protected fields are configured that may not be entered by operators during the operation of the machine. If the sensor recognizes an unauthorized intrusion into the protected field, for instance a leg of an operator, it triggers a safety-directed stop of the machine. In some cases, additional warning fields are positioned in front of the protected fields to prevent a person from a protected field infringement in good time or to reduce the working speed of the machine as a precaution. Protected fields have to be configured as relatively large to satisfy all conceivable cases so that a system reaction that reduces productivity occurs at a comparatively early time.
Protected fields in addition do not permit any close cooperation with machines, in particular with robots (HRC, human robot collaboration). Relevant standards in this connection are, for example, ISO 10218 for industrial robots or ISO 15066 for collaborative robots. Safety distances should be configured as small as possible in HRC and possibly even in a situation adapted manner, naturally with the proviso that safety is maintained. Standards ISO 13854, ISO 13855, and ISO 13857 deal with the establishment of safety distances.
An evaluation of objects and machines with respect to speed and to mutual distance is called “speed and separation monitoring” in said robot standards. It is expediently not the distance from the machine itself that is measured here. This would be too complex and too dynamic and a sufficient safe distance from future machine positions should also be observed. It is therefore sensible to predefine a hazard zone that surrounds the machine, that is a spatial region or a volume within which the machine carries out work movements. A hazard zone around all machine positions that the machine reaches in its work routine as a rule, however, has to be configured as so large that close cooperation between a human and a robot is still not possible.
DE 10 2005 054 359 A1 discloses a safeguard for a vehicle having an optical sensor. The direction of travel and the speed are determined by locating objects by means of the optical sensor and one protected field is selected from a plurality of stored protective fields in dependence on these parameters. At least two hazard zones for a harvester are defined in WO 2015/177 188 A1 among which one is selected in dependence on travel parameters.
In DE 10 2007 014 612 A1 hazard zones at a power-operated textile machine are monitored. A dynamically spatially variable protected zone can be formed by a select activation of spatially fixed monitoring means.
EP 1 635 107 B1 uses parameters supplied from a machine control for the fixing of a protected field called a danger zone.
In EP 2 315 052 B1 a specific hazardous object is recognized with reference to its geometry or to its movement behavior. Protected fields are then adapted to the movement of this hazardous object or a switchover is made between a plurality of protected field configurations.
EP 2 395 274 B1 fixes safety zones in dependence on the movement behavior of an object in an operating zone.
Said documents thus pursue various approaches to dynamically adapt protected fields; however, the general disadvantages of protected fields cannot be overcome by them and are also not even addressed.
EP 3 200 122 A1 discloses a 3D sensor with a safe recognition of objects in which the depth map is evaluated by a fine and by a coarse detection capability. Finely detected objects within an environment of a coarsely detected object are assigned to it, isolated finely detected objects are ignored as interference. This makes it possible to filter small objects determined downstream as not safety relevant, but otherwise does not contribute to advancing the securing of hazard zones.